Over the life of wind turbines there are several tasks that must maintain fixed the rotor in a certain position.
One of these tasks is the rotor locking to ensure it does not rotate which is needed to perform certain maintenance activities. Rotor locking systems typically comprise one or more pins (often two pins) which are pushed into holes in the stationary part of the wind turbine to prevent rotation of the rotor and therefore require a system to position the rotor so that the pins are perfectly aligned with the holes. The rotor locking process is difficult and time consuming. This task is even more complex when the wind speed increases and become impossible above certain wind speed.
Another of these tasks is the access of service personnel transported by helicopters to offshore wind turbines that have helihoist platforms where is needed to have the rotor stationary while the helicopter is nearby.
Another of these tasks is the calibration of the blade load sensors where the rotor shall be maintained fixed in various positions (and also having the blades at different pitch angles in each position) to compare the calibration with the static moments in said positions.
All these tasks must be performed in narrow ranges of time and within a wide range of speeds.
Known rotor positioning systems for such tasks have a high manual component and do not therefore allow a remote operation which would be very desirable especially in offshore wind turbines.